Normally being online is a better practice to have. But in this case good work king. Right track has allow damage from non direct hits which is why it dies and left does not. This do indeed be a bug.
#The Mk19 Can Disable ONLY The Right Track On Specific Tanks
viscid swallow
Its also anything that deals hat or heat splash damage thats affected by the bug. Seems like other tanks have splashed allowed on all so this actually makes t72 stronger technically drive with left side facing enemy lol